Aftermarket rear control arms - Boxed or tubular?

[Squid4life]

Researching and slowly collecting parts for my next T or GN, and looking at UMI suspension pieces. Had their tubular front uppers and lowers on my white T and LOVED them. Amazing pieces. My next car will more than likely have them. So, researching the rear control arms and am pretty sure I want the adjustable uppers, and non-adjustable lowers. (adjustable uppers and lowers seems a little much for my purposes) Their tubulars and boxed both have sway bar mounts, and are both .120" wall, so they are even in those aspects, but curious which would be better. Car will have wider wheels on back, and more than likely drag radials too. Sooner or later the car will end up with one of my Stage II's I have laying around so it should make a few horsepower. Tubulars seem lighter, but I would think boxed would be stronger and not flex as much if putting some power to them or pushing them in a turn. What are your thoughts? Here are the two I am considering:

http://www.summitracing.com/parts/upi-301517-b/overview/year/1987/make/buick/model/regal

http://www.summitracing.com/parts/upi-302117-b/overview/year/1987/make/buick/model/regal

 

[Chuck Leeper]

"but I would think boxed would be stronger and not flex as much if putting some power to them or pushing them in a turn."
We did some stress coat tests on the lowers we used to build, vs the boxed stockers.
The stockers were "weak sauce" around the area that the bushings press into.
My next set will be:
Uppers, tube, adjustable, w/ Spohn joints at the ft.
Lowers will have poly bushings in the rear, Spohn joints in the ft. [Also using adj ft mount boxes.]
The Spohns eliminate the twisting loads caused by axle movement on corners, driveways, uneven pavement, etc.

http://www.spohn.net/shop/Del-Sphere-Pivot-Joints/
Suspension parts: http://www.spohn.net/shop/1978-1987-GM-G-Body/Suspension/

Just sayin...

 

[83hurstguy]

You could turn your brain into mush reading internet arguments about the cross sectional properties of rear control arms. It won't matter... either aftermarket shape is way stronger/stiffer than stock. As Chuck mentioned above, put more effort into determining what type of bushings will work best for you. Poly on both ends of a converging 4 link is straight line only stuff in my opinion. I've had rod ends on the uppers, they amplify any gear noise into the rear frame crossmember, will eventually buzz as they wear if you put a lot of street miles on them (I got up to about 4k-5k and it drove me nuts). Finding the middle of the road Delsphere/Johnny Joint/Roto joint arm is typically the way to go for a street car. I have no experience with the DSE arms, though I haven't heard any complaints. They use a rubber bushing end with swivel link for rotational compliance.

 

[Squid4life]

Good info there guys, truly appreciate the input. I want to do things right on this next car, and not just use the "cheapest, better than stock" type parts. I want them to work correctly for all environments and movements, so the bushing/joint info is very helpful!